SCN Found in Cass, Clay Counties
September 18, 2006
White females (small arrows) of SCN on soybean roots are visible to the naked eye, but are still very small, no bigger than the head of a pin. They shouldn't be confused with nitrogen-fixing nodules on soybeen roots (large arrow) which are much larger and are more pink/brown in color. Photo: North Central Soybean Research Program Plant Health Inititative.
A soybean field in Cass County near Argusville, N.D., was confirmed by NDSU plant pathologist Berlin Nelson this summer as being infested with Soybean Cyst Nematode. This is the first confirmation of SCN in Cass County. The field apparently had a fairly high population of SCN, and most likely has been infested for a few years.
Richland County was the first and only county in North Dakota with confirmed SCN prior to this find. Across the river in Minnesota, SCN was confirmed in Clay County for the first time this year as well. A map that shows SCN confirmations in other states is available at the North Central Soybean Research Program Plant Health Initiative website: www.planthealth.info/scn_dist.htm.
The plant-parasitic nematode is a microscopic roundworm, which leaves eggs in the soil that can remain viable for years even in the absence of a suitable host. SCN feeding on the soybean root system may reduce N-fixing nodules, and result in increased susceptibility to a number of soybean diseases, including sudden death syndrome.
Yield losses up to 30% have been measured from SCN. Hot, dry weather may be conducive for plants to show the above-ground symptoms of SCN infection such as stunting, yellowing, and premature death.
SCN was first reported in North America in 1954, in North Carolina, and has since spread to 28 soybean-producing states and Canada. In Minnesota, SCN was first detected in 1978 near Frost in Faribault County. By 2000, its presence had been detected in 52 counties in the state, according to the U of M.
Once established, SCN cannot be eradicated; it can only be managed, says Carl Bradley, extension plant pathologist at North Dakota State University. The keys to management are good crop rotation practices no more soybeans on soybeans and the use of adapted resistant varieties. There are currently a little more than a handful of SCN resistant varieties that are adapted to our growing conditions and maturity, but more are on the way.
Dry edible beans are also a host of SCN, although more information on susceptibility and yield loss on dry bean is needed.
The Plant Health Initiative has an excellent SCN Management Guide online at www.planthealth.info/scnguide that includes scouting, management, and sampling information.
Fall good time for sampling SCN, other factors
While soil samples for SCN may be collected at any time, the ideal time to sample is as close to bean harvest as possible. SCN numbers tend to be highest when the plants are almost mature to shortly after harvest. Other factors might be analyzed in the soil test sample as well, such as nutrients, pH and soil organic matter. Sampling near harvest provides information and enough time for variety selection or choosing alternative crops for the next year.PO Box 5012, Fargo, ND, 58105, ph 701.231.7854, email: email@example.com, www.ag.ndsu.nodak.edu/diaglab.
The weather is usually more cooperative for fall soil sampling than in the spring, and the information helps in fertility and crop planning for the following year. Note that with the drought conditions in many areas of the Plains, its important to get a handle on the level of unutilized nutrients that may have been left in the soil from poorly developed or failed crops.
Local agronomists and county extension agents/educators are an excellent resource to guide soil sampling. The following plant labs conduct plant/soil test analysis; contact the lab for instructions before submitting samples.
NDSU Waldron Hall, Room 206,
1902 Dudley Ave., St. Paul, MN 55108, 612.625.3101 http://soiltest.coafes.umn.edu.
UM - Soil Testing Laboratory,
SDSU Oscar E. Olson Biochemistry Labs, Brookings, ph 605.688.6172, http://anserv.sdstate.ed.
Agvise Laboratories www.agvise.com, Northwood, N.D., ph 701.587.6010, Benson, Minn., ph 320.843.4109.
Link to more private and public testing labs can be found online at www.mda.state.mn.us/appd/soilabs.htm and www.motherearthnews.com/directory/soil_test.